The invention relates to an endoscope provided with a guide tube assembly for guiding a treatment instrument such as a forceps.
As is well known, an endoscope comprises a body, and a flexible insertion tube extending from the body. The distal end portion of the insertion tube is formed as a bendable portion. A rigid member, having an inspection window and an illumination window, is attached to the distal end of the bendable portion. When the flexible insertion tube is to be inserted into a body cavity, the insertion tube is bent in accordance with the configuration of the body cavity, and the bendable portion is bent by a remote control through a manipulation member mounted on the body.
The endoscope is provided with a guide means for guiding an elongated treatment instrument such as a forceps. The guide means has an inlet formed at the body, an outlet formed at the rigid member, and a guide tube assembly constituting a guide channel interconnecting the inlet and the outlet. The treatment instrument is inserted into the guide channel via the inlet, and is passed through the guide channel and the outlet, and is directed toward the body cavity. While observing the body cavity by the endoscope, the inner surface of the body cavity is treated by the treatment instrument.
A guide tube assembly shown in FIG. 2 of Japanese Laid-Open (Kokai) Utility Model Application No. 18102/87 comprises a resin tube, and the internal bore of the resin tube serves as a guide channel. A spiral groove is formed in the outer peripheral surface of the rein tube, and a reinforcement coil of steel is received in the spiral groove. Because of the provision of the spiral groove, the resin tube is considerably flexible. The reinforcement coil serves to prevent the resin tube from being deformed or crushed radially when the resin tube is bent. Since the reinforcement coil per se is flexible so as to be bent longitudinally, that is, in the direction of bending of the guide tube assembly, the reinforcement coil will not affect the flexibility of the resin tube. However, there is a possibility that the reinforcement coil may become disengaged or dislodged from the spiral groove.
In a guide tube assembly shown in FIG. 1 of the above Japanese Laid-Open Utility Model Application No. 18102/87, a resin for retaining purpose is filled in the spiral groove in the resin tube to thereby prevent the reinforcement coil from becoming disengaged from the spiral groove. However, the use of such retaining resin lowers the flexibility of the guide tube assembly.
Furthermore, in the above two guide tube assemblies, the resin tube and the reinforcement coil (as well as the retaining resin in the latter type) are considerably axially expansible. Therefore, as a result of a repeated bending of the guide tube assembly caused when bending the bendable portion of the endoscope, there is encountered a problem that the guide tube assembly remains expanded axially. The guide tube assembly, when thus expanded axially, is loosened within the insertion portion or the bendable portion, which results in a problem that the front end of the treatment instrument may be caught by the inner surface of the resin tube. This not only prevents a smooth guiding of the treatment instrument, but also may damage the resin tube.
Japanese Laid-Open Patent Application No. 66342/80, Japanese Laid-Open Utility Model Application No. 133001/86 and Japanese Utility Model Publication No. 40002/84 disclose guide tube assemblies similar to the above-mentioned guide tube assemblies.
Japanese Laid-Open Utility Model Application Nos. 53789/76, 177801/85 and 92603/88 disclose structures in which opposite ends of a guide tube are connected to a body and a rigid member, respectively.
Japanese Laid-Open Patent Application No. 36/84 discloses a braid tube woven of a metal wire and a resin yarn. The braid tube constitutes an insertion tube of an endoscope to be inserted into a body cavity.